1. Field
Exemplary embodiments of the present invention relate to a photo detection device, and more particularly, to a photo detection device in which a specific wavelength region to be detected can be easily controlled by controlling an energy bandgap of a band-pass filter layer, and the tilt of a cut-off wavelength can be controlled using a reactivity tilt control layer.
2. Discussion of the Background
In a conventional semiconductor photo detection device, the semiconductor photo detection device is mounted on a package and a band-pass filter capable of transmitting only a specific wavelength is coated on a cover for protecting the semiconductor photo detection device, in order to detect a specific wavelength.
The cover is made of sapphire, crystal, or tempered glass, having excellent transmissivity and a high resistance to damage. In the band-pass filter, materials having excellent light penetrability, such as quartz, are used as coating materials in the form of a circle or a rectangle.
For example, in order to increase ultraviolet (UV) transmissivity, multiple layers made of MgF2, TiO2, or SiO2 are coated on one surface of the filter, and UV coating materials having a high refractive index or a low refractive index are coated on the other surface of the filter.
The UV coating materials having a high refractive index may include any one of HfO2, Sc2O3, YbF3, Y2O3, ZrO2, NaF3, Al2O3, and Sb2O3. The UV coating materials having a low refractive index may include any one of SiO2, ZnSe, Sc2O3, and ZnS.
The cover on which the filter fabricated as described above has been deposited transmits light having only a specific wavelength band. In general, the cover is expensive because it involves the filter manufacturing process. Furthermore, the cover is problematic in that it is generally necessary to strictly classify the direction of a surface on which the cover is mounted, when the cover is assembled, because coating on the front of the cover is different from coating on the back of the cover, thereby decreasing productivity.
The cover is also problematic in that it is difficult to secure reliability because the cover responds to wavelengths other than a specific wavelength region, when a surface of the cover is scratched.
In order to solve these and or other problems, a package capable of detecting light of a specific wavelength region without an additional coating on a cover has recently been developed.
For example, resin that transmits only a specific wavelength region is filled in a package over a photo detection device, without installing a cover.
The resin may be, for example, an epoxy resin. In general, the resin consists of two types of liquid components, that is, a polymer and a hardener. Here, a transmittance wavelength of a resin depends the mixture ratio of materials of the polymer.
Such products are commercially sold. For example, Phenyl Si epoxy series by Shin-Etsu Chemical Co., Ltd. have a cut-off wavelength of about 300 nm.
Epoxy resin, in which a specific substance is mixed so that it serves as a band-pass filter for a specific wavelength region as described above, is problematic in that the UV reactivity of a package is low if the package is exposed to strong UV source for a long time, because a yellowness phenomenon is generated.
Furthermore, the flatness of a surface in which the epoxy resin is formed has a direct connection with light detection efficiency. There is a problem in that a light detection characteristic is slightly changed because overall flatness is low in a surface or at the package interface, when the polymer and the hardener are hardened by putting them into the package. Such problems may reduce the reliability of a product.